Insulating and lead anchoring means for transformers



Oct. 28, 1958 w. l... R. HENDERSON ETAL 5 INSULATING mo LEAD ANCHORING usms FOR TRANSFORMERS Filed Nov. 12. 1953 Inventors.- Wayne LR. Hendersqn,

Harry J Pr'qxmlr'q y 1 His Attbrneg.

United States Patent INSULATING AND LEAD ANCHORING MEANS FOR TRANSFORMERS Wayne L. R. Henderson and Harry I. Proxmire, Fort Wayne, Ind., assignors to General Electric Company, a corporation of New Yorlr Application November 12, 1953, Serial No. 391,635 2 Claims. (Cl. 336-209) This invention relates to transformers and more particularly to improved coil insulating and lead anchoring means for use in transformers.

It has been found, with respect to coils for use in small transformers, that by precision winding the coils less material is necessary to achieve the same effect as where the coils are not so wound. Precision wound coils are generally formed on an arbor without any insulation between the coils except for the actual insulating coating on the wire forming the coils. Each individual turn of wire fits into'the groove formed by the two adjoining turns of wire of the layer directly below the one being formed. Because of their advantages such coils have been used extensively; however, the problem of adequate insulation of the coil from the transformer core has been difficult to solve economically. A common practice heretofore has been to provide insulating material on the sides of the coil only and not between the. coil and the core, the air space being depended upon in that location for proper insulation. However, this construction may permit arcing to occur between the inner edge of the coil and the inner edge of the core. This results generally because the insulation at the side of the coil and the insulation around the center leg of the core do not meet completely. Another difficulty encountered in the manufacture of transformers has been the'presence of tension on the transformer coil leads. Such pulling results in a lessening of the diameter of the lead wire which, while small, can decrease to a noticeable degree the conductive ability of the wire. In addition the lead may be pulled tight around a corner of the coil thus creating the danger of short circuits. In view of the above it is desirable to provide positive insulation at all points between the coil and the conductor and to prevent the application of tension to the coil leads.

An object of this invention is, therefore, to provide an improved transformer construction which prevents the undesirable occurrences described above.

Further objects and advantages of this invention will become apparent and the invention will be better understood by reference to the following description and the accompanying drawing; the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

This invention in its broadest aspects provides a single piece of sheet material, preferably flexible with good insulating qualities and shearing strength. This sheet is bent around the coil so as to insulate it from the top and sides of the core. A tab is cut in each side of the sheet and is folded under the coil between the coil and the center leg of the core to thereby completely insulate the coil and the core from each other at that part of the coil which is adjacent both the center leg and the side of the core. The top of the folded sheet is provided with openings, and the external lead to which the coil lead is attached is threaded through these openings. The

2,858,514 Patented Oct. 28,

openings are placed close enough together so that tension on the outside lead would tend to shear the insulating material before the lead were to slide through the openings and place tension on the coil lead attached thereto.

In the drawing:

Fig. 1 is a view in perspective of a transformer utilizing the improved insulating means of this invention;

Fig. 2 is a developed view in perspective of the insulating means of Fig. 1 before they are f ormed around the coils;

Fig. 3 is a fragmentary side view of a transformer utilizing the novel insulating means; and

Fig. 4 is a fragmentary cross-sectional view along the line 4-4 of Fig. 3.

Referring now to Fig. 1 of the drawing, there is shown a transformer which may be of the high reactance type having autotransformer connections as indicated generally at 1. It will be understood that this type of transformer is used merely for illustrative purposes and is not a requisite part of the invention. Transformer 1 has a core 2 of any standard type made up of laminations 3. The core shown is of the shell type and is made up for illustrative purposes of three parts, outer yoke parts 4 and 5, and a center leg 6 which is maintained between the two outer parts 4 and 5. Center leg 6 is encased on all four sides in a spool 7 of insulating material which extends from the inner side 8 of end leg 9 of the core 2 to the inner side (not shown) of the other end leg 11. Placed on center leg 6, and separated therefrom by insulating spool 7, are a primary coil 12 and a secondary coil 13. Coils l2 and 13 are precision wound, that is, no insulation is used in their manufacture except for the insulating coating on the wire forming the coils. Leads 14 extend from each of the coils 12 and 13 and are respectively connected at 15 to external leads 16. Insulating pieces 17 and 18 of this invention are respectively placed around coils 13 and 12 as shown.

Referring now to Fig. 2, insulating pieces 17 and 18 are shown before being folded around coils 13 and 12 respectively. Pieces 17 and 18 are alike except insofar as the width of center section 19 and the number of openings 20 and 33 are concerned. Like numerals have been given to like parts in pieces 17 and 18, wherefore a description of piece 17 will clearly show the construction of piece 18 also.

Piece 17 has two cuts 21 at each side extending in as far as folds 22. Fold 22 and fold 23 determine an area 24 at each side of piece 17 and the two folds 23 determine area 19 between them. Openings 20 and 33 are provided in pairs preferably close together and at a small distance from the edge 25 of piece 17. Directly in line with each pair of openings 20 is a notch 26 cut into side 25 of piece 17.

The two cuts 21 at each side of the piece determine. together with crease 22, an area 27 in each corner of the piece and a tab 28 in the center of each end of the piece. Cuts 21 permit tab 28 to be folded at any angle to area 24 independently of areas 27.

Referring again to Fig. 1, it will be seen that the pieces 17 are so placed on coil 13 that areas 19 cover the edges of coil 13 thereby insulating it from yoke parts 4 and 5 of core 2. The areas 24 are folded down at substantially right angles to area 19 to cover the sides of coil 13 and provide insulation between the sides of the coil and the end legs 9 of core 2. It will clearly be seen however that areas 24 have been so formed as to extend only to as far as center leg 6 of core 2. Areas 27 form extensions of area 24 in the same plane therewith. Thus, the entire width of areas 27 extends past the edge of center leg 6. This, in turn, means that the same is true of area 28. The presence of slots 21 will now, permit area 28 of piece 17 to be folded inwardly 3 under coil 13 between it and center leg 6 which is covered with insulating spool 7. As appears most clearly in Fig. 3, area 28 now completely insulates the inner edge of coil 13 from the inner side it of and leg 9 of core 2. Together with insulating spool 7 this provides complete and positive insulation all the Way around the inner surface of coil 13 from all adjacent parts of core 2.

Referring to Fig. 2 the purpose of openings 20 and 33 will now be explained. it is seen that lead 16 passes down through the hole 33 and up again through hole 20. Referring back to Fig. 1 it will be observed that coil lead 14 is attached to the end 29 of lead 16 projecting from hole 20. It will now be seen that if for any reason tension is placed on lead 16, as at 30 in Fig. 4, the'sharp bend at 31 that is necessary to pass lead 16 through holes 20 and 33 will cause all the strain to be put on insulating piece 17 and will substantially avoid movement of end 29 to which coil lead 14 is attached. Notch 26 is cut in piece 17 directly in front of holes 20 and 33 to provide a guide for leads 14 and to seat them properly. It will be understood of course that it is necessary to utilize holes 20 and 33 only in one of each pair of pieces 17 around a coil 13 but that to provide for economy in manufacturing both pieces 17 are made with holes 20 and 33 although these holes may be utilized on only one of each two pieces.

It will be seen from the above description that I have provided an insulating piece which performs the double function of insulating coil 13 from core 2 at all points and in addition securely anchors the external leads to the transformer so that no tension will be placed on the coil leads as a result of tension on the external leads.

It will be understood that all the features of piece 17 which have been described pertain equally to piece 18 which is included to show the modification necessary for a different size of coil having more leads.

While this invention has been explained by describing a particular embodiment thereof it will be apparent that improvements and modifications may be made without departing from the scope of the invention as defined in the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A transformer having a core with a winding leg and a coil mounted thereon, said coil having at least one lead extending therefrom; means for insulating said core from said coil comprising a member formed of pliable sheet insulating material, said member comprising an area covering a portion of the peripheral surface of said coil, said area having a width substantially equal to the width of said coil, said member having portions folded down over each side of said coil so as to have an area covering a part of each side of said coil, said folded portions having a length in excess of the width of the side of said coil, said portions each having a pair of slots fanned in the end thereof defining a tab portion, each of said tab portions being folded under said coil and projecting toward each other between the same and said winding leg, said first named area of said member having at least one pair of openings formed therein relatively close together and relatively close to the edge of said member, said openings being in a line substantially normal to said edge; and an external electrical lead threaded through said openings and having an end connected to said coil lead whereby any tension exerted on the other end of said electrical lead will be transmitted to said member instead of to said coil lead.

2. A transformer having a core with a winding leg and a coil mounted thereon, said coil having at least one lead extending therefrom; means for insulating said core from said coil comprising a member formed of pliable sheet insulating material, said member comprising an area covering a portion of the peripheral surface of said coil, said area having a width substantially equal to the width of said coil, said member having portions folded down over each side of said coil so as to have an area covering a part of each side of said coil, said folded portions having a length in excess of the width of the side of said coil, said portions each having a pair of slots formed in the end thereof defining a tab portion, each of said tab portions being folded under said coil and projecting toward each other between the same and said winding leg, said first area of said member having at least one notch formed in an edge thereof and at least one pair of openings formed therein relatively close together and relatively close to said notch, said openings and said notch being in a line substantially normal to said edge; and an external electrical lead threaded through said openings and having an end connected to said coil lead whereby any tension exerted on the other end of said external lead will be transmitted to said member instead of to said coil lead, said coil lead being seated in said notch.

References Cited in the file of this patent UNITED STATES PATENTS 1,797,768 Goad Mar. 24, 1931 1,908,728 Bollmann May 16, 1933 1,992,814 Cooney Feb. 26, 1935 2,015,981 Welfield Oct. 1, 1935 2,229,373 Cole Jan. 21, 1941 2,243,533 DEntremont May 27, 1941 2,275,967 Keillor et al. Mar. 10, 1942 2,289,992 Petersen July 14, 1942 2,339,088 Marsh Jan. 11, 1944 2,573,600 Pruehs Oct. 30, 1950 2,652,521 Westphal Sept. 15, 1953 

